Figure 3.

Models of autodephosphorylation. A modeled water (grey sphere) was placed into the crystal structures of wild type CheY and the position T+1 mutants bound to BeF₃ (light blue and yellow) to assess how various residues at this position might influence an attacking water molecule. Contacts between the modeled water and position T+1 (residue 88) were calculated using Reduce and Probe ⁷⁹. Hot colored spikes (yellow, red, and hot pink) indicate van der Waals clashes, whereas lime green colored dots indicate hydrogen bonding interactions. (A) Ala at position T+1 does not interact with an attacking water. (B) β-branched residues like Val and Ile at position T+1 would sterically block an attacking water molecule. (C) The small polar residues Ser and Thr could contribute a hydrogen bonding interaction, as shown for CheYA88S. In the crystal structure of CheYA88M, the Met at position T+1 was observed in two conformations, one that would block an attacking water molecule (D) and one that minimally interacted with the modeled water molecule (E). A hydrogen bond between Asn59 and Glu89 is shown as a green dashed line when present.